Samoans will have to start paying a hefty fee to fly on Samoa Air if they're overweight.

Samoa Air is the first airline to make customers pay as much as they weigh when flying on the airline. For overweight customers, this could mean big charges.

"This is the fairest way of travelling," said Chris Langton, chief executive of Samoa Air. "There are no extra fees in terms of excess baggage or anything – it is just a kilo is a kilo is a kilo."

Customers will have to start typing in their weight when purchasing Samoa Air tickets online, and pay anywhere from about $1 to about $4.16 per kilogram (depending on whether they're traveling short domestic routes or between Samoa and American Samoa).

Once arriving at the airport, the customers are weighed again to make sure they didn't lie online.

Why is Samoa Air doing this? According to Langton, it's partially meant to raise awareness of obesity and health, since Samoa is often in the top 10 lists for obesity.

"When you get into the Pacific, standard weight is substantially higher [than south-east Asia]," said Langton. "That's a health issue in some areas. [This payment system] has raised the awareness of weight."

The payment by weight system will have other benefits, such as safety measures where a plane can only handle so many overweight customers (larger passengers have to be evenly distributed on the plane for safety); families with young children could pay much less than what they're paying now, and carriers could gain the money lost on fuel for carrying heavier passengers.

The economics of airfares are clearly not directly driven by direct cost. The price for the same seat varies wildly, depending on when you buy the tickets, etc. Also, the cost to fly the same itinerary will vary wildly based on which airline you use, when you buy etc.

Note this: I might buy a ticket with 3 stops that requires multiple flights over a long distance, and that ticket might well be hundreds of $ cheaper than a direct flight that covers many fewer miles. So, clearly direct costs are not the determinant of ticket prices.

So, in this environment, the variation in passenger weight seems like a pointless way to determine ticket prices. Also: if I check a bag, I might pay an extra fee. If I carry the same bag onto the flight, I don't pay the fee. The weight is the same.

quote: Note this: I might buy a ticket with 3 stops that requires multiple flights over a long distance, and that ticket might well be hundreds of $ cheaper than a direct flight that covers many fewer miles. So, clearly direct costs are not the determinant of ticket prices.

You're missing the obvious point of such pricing: the lower cost is to decrease under-utilization of the multi-hop routes while keeping high margins on -hopefully- fully-utilized direct routes.

Direct costs are -not- just the cost of flying your body weight X miles; they include the plane's weight & cost and staff costs. Such route-shifting helps justify (subsidize) flights on under-utilized routes and increases overall destination-capacity without requiring additional planes and gates.

The challenge of airlines has always been to optimize utilization. Customers have long suffered from their overbooking -- their desperate efforts to statistically project cancellations. When it seemed a growth industry we were spoiled by excess capacity created with that growth in mind. They've dealt with today's market by limiting capacity, making those indirect routes important even when we'd pay for direct ones.